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Old 12th January 2012, 10:22 AM   #1531
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Originally Posted by slowlearner View Post
Wow, you engineering knuckleheads sure know how to put a damper on an exciting thread
I might assume that no one is going to be pleased by a misleading commercial & the thread is about class D amplifier I believe?

Class D is a digital amp that is not workable without DSP does not matter if it has global analogue feedback around or not.

Also claims that PWM amp with switching frequency 300-450KHz can sound as good as HiEnd tube amp while some of tube amps have bandwidth up to 300KHz-500KHz is a an extremely optimistic approach (not realistic from a technic point of view to make it clear).

However it does not mean that all that related to NCORE in particular or NCORE is not an exciting item.

The general discussion regarding class D amplification was started by a link to an external web page with some (IMHO) very provocative general statements.
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Old 12th January 2012, 10:39 AM   #1532
Julf is offline Julf  Europe
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Originally Posted by andyjevans View Post
Audio is sound and all sound is detectable
I guess it depends on how you define "sound" and "detect".

Do you detect the sounds of bats?

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I want to hear sound that is as close as possible to the timbre and tone colour of live instruments. Engineering is only a means to that end.
I think we are in total agreement on this one.

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I still believe that audio is sound - not engineering. Spookily enough, that's what the word means.
Well, yes, the word "audio" means sound. So anything having to do with sound. But when used in a context like the name of this forum, it usually means the recording and reproduction of sound. Producing the sound is art, artistry and skill. Reproducing it is technology, and technology is engineering and applied science. For that you do need the tools and skills of the engineer and the scientist, and measurements are important tools.
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Old 12th January 2012, 10:49 AM   #1533
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Suntechnik:

Bruno's (and most other) Class-D amplifiers use an analog signal. It matters not that this analog signal is the duty-cycle of a switching waveform, rather than a changing voltage or current. The duty cycle is still a non-quantised analog representation of the audio waveform. It is NOT a digital signal.
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Old 12th January 2012, 11:41 AM   #1534
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@suntechnik. Go easy on the "IMHO". Your opinions have no semblance of humility whatsoever. You have the most extreme phenomenal gall to try and teach me what class D amplifiers are.

Here's my last polite reply to you (as "polite" goes). Think about this: imagine an engineer who was trained to think mainly in current terms and only sparingly in voltage terms (the opposite of how engineers mostly think). Imagine his oscilloscope had current probes attached and the only voltage probe in the lab was in a cupboard gathering dust. That engineer would have no problem whatsoever designing or testing circuits. The current/voltage duality allows this. This engineer, when studying the signals in a class D amplifier would never see square waves. Instead he would see a continuously variable current alternately conducted by a pair of FETs. The idea of associating this with "digital" wouldn't even occur to this person. Therefore, the association with digital is dependent upon one's point of view. It is subjective. The fact that people think of class D as digital is an artefact of the fact that we mostly think and measure in voltage terms.

Now, I have noticed that you have made no attempt to respond to any of the replies that were given to your previous post. It is extremely disrespectful to expect people to listen to you without bothering to even read their replies in return and respond cogently. You are now simply restating your position and moving on to other items (now it's suddenly bandwidth). This is a one-way conversation: you yelling at the top of your voice with your ears plugged. This is not the behaviour of someone who wants to communicate. It is the behaviour of someone intent either on causing trouble or pressing his view.

I am calling troll.

Other than that, how come you have such strong views? Have you ever built any class D amplifiers yourself to learn about them and to test your views? No? Then eff off.
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Last edited by Bruno Putzeys; 12th January 2012 at 11:48 AM.
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Old 12th January 2012, 11:59 AM   #1535
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@andyjevans: I have the impression we don't disagree much.

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Audio is sound and all sound is detectable, because human hearing can pick up very tiny differences - this has been known since 1860 and Wundt's psychophysics experiments with the threshold of perception in Leipzig. The "measurements are everything" argument runs the risk of becoming the old "operation successful, patient died" argument.
At the peril of boring people to death, I am constantly pointing out that the "measurements are all" argument can only be valid when one is prepared to accept that an established set of measurements is probably incomplete. At that stage you have to use your ears to find out if things are happening your measurements didn't predict and then refine the measurements. It all starts with ears. If not, what basis would we have to set the standards we want to meet? We have to start by figuring out what is audible. For instance, if we didn't, how would we know what bandwidth is required? Would 15GHz suffice? 100MHz perhaps? How much distortion can we tolerate? Without starting at the ear, well-meaning designers could end up building ampifiers with 5% distortion and a 500kHz bandwidth and think that because of that bandwidth it must really be a good amplifier. Most of the things we need to know about audibility is by now quite firmly established. A handful of things aren't. For that handful of things you have to do listening tests. For the remainder thankfully we don't.

I think one of the reasons why I like to hammer on the measurement nail is precisely your starting point: really subtle things count. It is weird to see people peddle amplifiers with high distortion figures and concomitant colouration and then find them claiming that some stuff is just too subtle to measure. If that isn't trying to have their biscuit and eat it I don't know what is...

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Originally Posted by andyjevans View Post
The ultimate arbiter for audiophiles who seriously want to re-create music in their home is how "musical" that sound is.
I presume you mean to say it's all they have to base their judgment on? That sounds about right If someone is put off listening by the sound of a particular amp I certainly hope he doesn't buy it. The problem is that when reviewers, who should be better equipped, do the same, you end up with the vicious circle I described with everyone using broken equipment. Once that starts happening in the recording end as well, the audiophile consumer will be the victim. He will have musicality only when his replay equipment plays ball with the equipment used during recording, mixing and mastering.

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Originally Posted by andyjevans View Post
I still believe that audio is sound - not engineering.
Ah well, the word "music" has multiple meanings too. It can be the actual acoustical output, it can be the act, it can be the score, it can be the study.
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Last edited by Bruno Putzeys; 12th January 2012 at 12:12 PM.
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Old 12th January 2012, 12:25 PM   #1536
Eva is offline Eva  Spain
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A class D modulator converts voltage information into time information. There is no quantization whatsoever. Time resolution of electrons (¿jitter?) is not worse than potential resolution (noise).

Then output stage and output filter perform the opposite conversion, time to voltage.

Someone that doesn't understand the amplitude-time-amplitude conversion has a long learning way to go before he can have a clue about electronics.

There is no inherent distortion involved in such a conversion, only bandwidth limitations (to Fsw/2, aliasing takes place for higher components). Any distortion component measurable at the output of a class D amplifier comes only from aliasing and the inaccuracy of the modulator to exactly mimic the "inverse" of the response of the output stage and filter, like in any linear amplifier... But this is something subject to continuous improvement, there is not a known "improvement ceiling".
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Last edited by Eva; 12th January 2012 at 12:34 PM.
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Old 12th January 2012, 12:30 PM   #1537
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Originally Posted by Bruno Putzeys View Post
@andyjevans: I have the impression we don't disagree much.

Ah well, the word "music" has multiple meanings too. It can be the actual acoustical output, it can be the act, it can be the score, it can be the study.
That's absolutely true! Well observed. We probably don't disagree much, and our goals are probably identical. I still think that audio is sound, and engineering is a means to that end, so it's just a question of how we phrase it.

Best

andy
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Old 12th January 2012, 12:31 PM   #1538
tinitus is offline tinitus  Europe
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Originally Posted by andyjevans View Post
I still believe that audio is sound - not engineering.
andy
both is fine
just dont call it science
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Old 12th January 2012, 12:34 PM   #1539
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Engineering is applied science
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Old 12th January 2012, 12:36 PM   #1540
damarfi is offline damarfi  Croatia
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He went through four generations of circuit boards without listening to any of them. Instead, he connected each board to an audio analyzer and then rejected it because the results weren't what he wanted. The fifth iteration, though, looked good. Just before Christmas 2001, he brought a pair of the amps home and connected them to the speakers in his living room. He put on a CD of Spanish classical music and selected a song by the 18th-century composer Juan Francés de Iribarren, ”Viendo que Jil, Hizo Raya.” He settled back in a chair and listened. It took him just a few seconds to reach a conclusion: ”Straight in the bull's-eye.”
This is citation from Bruno's interview 2008 and up to me it shows how somebody who has knowledge and love to music (and sound) enthusiastically build amps. Ears - measurements - ears is only way to make musical equipment.

Bruno Putzeys: The Sound Of Music (Extended Play) - IEEE Spectrum
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